The present invention relates to a printing apparatus and printing method and, more particularly, to a printing apparatus and printing method for printing by scanning a print medium by a carriage which supports a printhead having a plurality of printing elements aligned in a predetermined direction, in a direction perpendicular to the alignment direction of the printing elements.
As an information output apparatus in a wordprocessor, personal computer, facsimile apparatus, or the like, there is a printer for printing information such as desired characters and images on a sheet-like print medium such as a paper sheet or film.
The printing method of the printer includes various known methods. In recent years, an inkjet method particularly is receiving a great deal of attention because the inkjet method enables noncontact printing on a print medium such as a paper sheet, easily prints a color image, and generates little noise. In terms of low cost and easy downsizing, the printer generally widely adopts a serial printing arrangement in which a printhead for discharging ink in accordance with desired print information is mounted, and printing is done while the printhead is reciprocally scanned in a direction perpendicular to the feed direction of a print medium such as a paper sheet.
The inkjet printhead generally comprises a plurality of printing elements (nozzles) for discharging ink that are aligned in the feed direction of the print medium (subscan direction). As the driving method, the printhead uses foaming energy generated upon driving an electrothermal transducer (heater) set in a nozzle, or uses shrinkage of a piezoelectric element set in a nozzle.
In any driving method, simultaneous drive of all nozzles decreases the print quality due to crosstalk between the respective nozzles, or it requires a large-capacity power supply because a large current temporarily flows. To prevent this problem, nozzles are divided into several blocks to execute time-division driving of time-sequentially driving the nozzles in units of blocks.
Print data is transferred for each data (column) in the nozzle alignment direction printable when the printhead simultaneously drives all the nozzles. In general, data of the next column are serially transferred while the current column is driven.
Recently, a higher throughput is demanded. To meet this demand, various methods are proposed and implemented. For example, one general method is to shorten the driving time-. However, a certain period of time is required in order to obtain foaming power enough to discharge ink droplets by driving a heater. The throughput cannot be so increased by shortening the driving time.
On the other hand, another method increases the number of nozzles aligned on a printhead and increases a print width printable by one scan. If, however, the number of nozzles of the printhead is increased, the number of data printed simultaneously increases, which prolongs the print data transfer time.
Still another method uses a high-speed print mode in addition to a normal print mode, and thins and prints print data to realize high-speed printing, as disclosed in Japanese Patent Application No. 11-204957. Thinning printing is realized by thinning driving blocks, so that the driving time is shortened. However, in a printhead having a large number of nozzles, the data transfer time is longer than the driving time, and the actual throughput does not increase as expected.
For this reason, sometimes the frequency of a data transfer clock is increased to shorten the data transfer time. Since data is transferred to the printhead via an FPC cable, the upper limit of the frequency of the transfer clock is about 10 MHz, and the throughput cannot be so increased.
Also in a print mode in which multipass printing is done by scanning the same printing region a plurality of number of times, print data is thinned and printed in each scan. Also in this case, the scan speed cannot be increased owing to the print data transfer time.
The present invention has been made in consideration of the above situation, and has as its object to provide a printing apparatus and printing method capable of shortening the print data transfer time and increasing the throughput in thinning and printing print data in a high-speed print mode, multipass printing, or the like.
To achieve the above object, according to the present invention, there is provided a printing apparatus for printing by scanning a print medium by a carriage which supports a printhead having a plurality of printing elements aligned in a predetermined direction, in a direction perpendicular to an alignment direction of the printing elements, comprising:
transmission means for serially transmitting print data to the printhead;
storage means for storing the print data transmitted from the transmission means in correspondence with the respective printing elements;
holding means for reading out and holding the print data stored in the storage means; and
driving means for driving the respective printing elements in accordance with the print data held in the holding means,
wherein when a print mode in which printing is performed only by some of the plurality of printing elements by one scan is selected,
the transmission means transmits print data corresponding to the printing elements used for printing, and
the storage means stores data transmitted from the transmission means at a speed which is a reciprocal multiple of a ratio of the printing elements used for printing.
To achieve the above object, according to the present invention, there is provided a printing method of printing by scanning a print medium by a carriage which supports a printhead having a plurality of printing elements aligned in a predetermined direction, in a direction perpendicular to an alignment direction of the printing elements, comprising:
the transmission step of serially transmitting print data to the printhead;
the storage step of storing the print data transmitted in the transmission step in storage means in correspondence with the respective printing elements;
the holding step of reading out and holding in holding means the print data stored in the storage means; and
the driving step of driving the respective printing elements in accordance with the print data held in the holding means,
wherein when a print mode in which printing is performed only by some of the plurality of printing elements by one scan is selected,
the transmission step comprises transmitting print data corresponding to the printing elements used for printing, and
the storage step comprises storing data transmitted in the transmission step at a speed which is a reciprocal multiple of a ratio of the printing elements used for printing.
More specifically, in a printing apparatus for printing by scanning a print medium by a carriage which supports a printhead having a plurality of printing elements aligned in a predetermined direction, in a direction perpendicular to the alignment direction of the printing elements, print data are serially transmitted to the printhead, and the transmitted print data are stored in correspondence with the respective printing elements. The stored print data are simultaneously read out and held, and the respective printing elements are driven in accordance with the held print data. When a print mode in which printing is done only by some of the plurality of printing elements by one scan is selected, print data corresponding to printing elements used for printing are transmitted, and the transmitted data are stored at a speed which is a reciprocal multiple of the ratio of printing elements used for printing.
With this arrangement, when the print mode in which printing is done only by some of the plurality of printing elements by one scan is selected, the processing speed in executing storage processing is increased to a reciprocal multiple of the ratio of printing elements to be used. For example, the speed of storage processing is doubled for a print mode using half the printing elements. Accordingly, the time necessary for data processing until the respective printing elements are driven after transmitted print data are received is shortened without changing processing subsequent to holding processing.
In thinning and driving nozzles in high-speed printing, multipass printing, or the like, the time required for print data transfer processing can be shortened without using any special control or complicated arrangement. This can more greatly increase the print speed.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.